The present invention relates to an ink occlusion material for writing utensils, particularly to an aqueous-ink occlusion material and a method for the preparation thereof.
Heretofore, as an ink occulusion material for writing utensils, there has been known a material prepared by impregnating a precondensate of a thermosetting resin such as melamine, epoxy or phenol resin in a fiber bundle of synthetic fibers such as polyester, Nylon, acrylic, vinylon or polyethylene fibers, and compressing and heating the bundle to adhere the fibers to form them into a shape. However, with use of the thermosetting resin in the occlusion material in which it is necessary to smoothly flow a liquid such as ink for writing utensils, the thermosetting resin hardly adheres uniformly to the fiber bundle so that the capillary structure useful for ink flow and ink occlusion becomes incomplete and the fluctuation of ink flow becomes high.
To improve such disadvantages, Japanese Patent Publication No. 37571 of 1975 discloses a method in which a mixed sliver of a plural of fibers having a different melting point is covered with a resin film having an approximately same melting point as them to effect hot melt adhesion. However, this method has a disadvantage that the ink utilization ratio is lowered as the resin absorbes ink.
As an alternative method, Japanese Patent Publication No. 16963 of 1970 discloses a method in which the fibers are paralleled in the axis direction and the resultant continuous fiber bundle is treated with an adhesive solution and then squeezed and the solvent is removed by drying to adhere and fix the fibers and then finally the periphery of the fiber bundle is covered with a polymer film to prepare an ink occlusion material. However, this method has defects that the step of adhering the film at the overlapping portion after covering the bundle with the polymer film can not be speeded up, the percent defective is high and resultantly it is not economical.
We, inventors, have already proposed a method in which crimped acrylic fibers are paralleled to the fiber axis direction and an organic solvent which can dissolve the fiber is applied on the resultant fiber bundle and the bundle is heated to melt-adhere at least a portion of the fibers in Japanese Patent Laid-open Publication No. 199698 of 1982. However, this method, in which the fiber is paralelled to the fiber axis direction, has defects that the fibers partially fall out in the squeezing guide of the organic solvent and during the drying procedure and the adhered spots are few unless the heating is carried out under compression. On the other hand, as acrylic fiber is more hydrophilic than polyester fiber, polyethylene fiber and polypropylene fiber, it retains much ink when an aqueous ink is used and thus the ink utilization ratio becomes low.
Furthermore, Japanese Laid-Open Patent Publication No. 60774 of 1986 discloses a method in which a fiber of low hydrophile such as polyester fiber is mixed in the fiber bundle to solve the problem of the above-mentioned Japanese Laid-Open Patent Publication No. 199698 of 1982. However, when polyester fiber, etc. is mixed uniformly, the ink utilization ratio can be somewhat improved but the ink retainability is lowered in order to get an enough ink utilization and the problem of fiber escape occurs.
An object of the present invention is to provide an ink occlusion material which has the same ink retention as in the case of using an acrylic fiber alone and yet shows a high ink utilization ratio and gives no problem of fiber escape and thus can be easily handled. Another object of the present invention is to provide a method for the preparation of such an easily handled ink occlusion material for the writing utensils easily in a commercial scale at a low price.